Recently, in the field of machine tools, it is desired to increase efficiency. As a way to increase efficiency, it is possible to increase the outputs of the driving motors for driving the feed axes and the spindle in order to increase the machining speed and to reduce the machining time. However, for this purpose, the strength of the constitutional members of a machine tool must be increased which result in an increase in size of the machine tool and reduction in tool life.
Further, in order to increase the efficiency of a machine tool, it is necessary to reduce the time period for changing processed and unprocessed workpieces. In order to change processed and unprocessed workpieces, an operator often needs to directly access machine tools, in particular compact machine tools. In such a case, the safety of the operator must be ensured.
Furthermore, in the field of machine tools, machining processes are becoming complex, whereby machine tools having four or more feed axes including one or more rotational feed axes as well as orthogonal three linear feed axes are becoming widespread. In machine tools having four or more feed axes, a workpiece is mounted directly to a rotary table or to a workpiece mount such as a rotary workhead or an angled mount secured to a rotary table. Therefore, when an operator carries out a preparation, removing a processed workpiece from and attaching a new unprocessed workpiece to the workpiece mount, if the rotational table unintentionally rotates, the preparation is obstructed and the safety of the operator is deteriorated. Thus, safety devices for securing rotational tables so as to prohibit the rotation thereof have been developed.
1 Japanese Patent No. 2918732
2 WO 2008/029486